In electronic AC transmission circuits it is often desirable to be able to detect, measure and monitor grounding faults and other imperfections which can be sensed by imposing a DC signal and monitoring the resulting current loss from the circuit. Such capability may be applied in any of a wide variety of applications, particularly in applications involving AC power supplies which must remain in service and cannot easily be powered down to allow for circuit testing. Such power supplies are typically found in large industrial electric motors, power supplies to large buildings, etc.
One of the principal obstacles to achieving this goal is the difficulty attendant to separating the imposed DC waveform from the AC waveform. The principal problem resides in the inability to provide sufficiently discrete means to accurately extract the DC waveform with sufficiently high signal-to-noise ratio to make measurement possible.
It is necessary to be able to isolate the DC source and detection circuitry from damage by exposure to high voltage AC waveforms.
It is also desirable to be able to monitor and measure impedance in AC circuits to determine where ground faults or other current drains might exist and to what extent. Furthermore, it is most desirable to be able to be able to do this while the AC circuit is active. This not only saves down time but can be used to monitor circuit degradation to be able to predict failure well before it occurs or has progressed to a degree that the system must be deenergized before it has reached a dangerous state. Such advance information allows one to anticipate when failure is likely so that provisions to be made for repair or replacement of all or part of a given electrical system.
It is also advantageous to be able to be able to perform operational monitoring to eliminate the need for operators to handle high voltage circuitry, as is the case where systems must be deenergized to allow for the use of megaohm metering devices ("meggers") to measure impedance.
In view of the present disclosure and/or through the practice of the described invention, additional advantages, efficiencies and solutions to problems may become apparent to one skilled in the relevant art.